U.S. Pat. No. 5,057,710 teaches electret materials comprising hindered amines, nitrogen containing hindered phenols or metal-containing hindered phenols.
U.S. Pat. No. 5,556,618 discloses antibacterial electret materials.
U.S. Pat. No. 6,123,752 teaches high efficiency filter medium containing a performance enhancing additive.
U.S. Pat. No. 6,743,464 teaches a method of making electrets through vapor condensation.
U.S. Pat. No. 6,969,484 discloses a method of making electret.
U.S. patent app. No. 60/791,047, filed Apr. 11, 2006, teaches electret materials comprising certain additives.
U.S. published app. No. 2005/0203226 and WO 2004/072168 teach trisamide nucleating agents.
Mohmeyer, et al., in Polymer, 48 (2007), 1612-1619, discusses electret materials.